For the purpose of materialography, materialographic specimens, i.e. pieces of a material such as metal, typically are cut by abrasive cut off wheels in, for example, materialographic cutting machines.
After a specimen has been cut, the specimen needs to be prepared for examination in one or more steps of grinding and or/lapping and/or polishing; often in a stepwise finer manner.
The grinding and/or polishing typically takes place in a dedicated grinding and/or polishing machine where the specimens are placed in a specimen mover configured for moving the specimens with respect the typically rotating preparation surface of the grinding and/or polishing machine.
The specimen mover typically is configured for applying a perpendicular force with respect to the preparation surface onto the specimens whereby the specimens are pressed against the preparation surface of the grinding and/or polishing machine.
In between each step of grinding and/or polishing the specimens, the specimens may need to be rinsed to remove coarse-grained debris and abrasives before the next and finer step of preparation. This to avoid contaminating the next step of grinding/polishing the specimen. The intermediate steps of cleaning the specimens may require removal of the specimens from the specimen mover and/or the grinding and/or polishing machine for the steps of cleaning the specimens.
U.S. Pat. No. 5,800,254 A discloses an automatic sample preparation system configured for polishing and grinding metallurgical samples prior to examination. The system includes a rack which holds a plurality of abrasive platens and a platen transfer mechanism for selecting a platen from the rack and transferring the platen to a drive plate for a polishing operation. The system further includes a polishing head which can be rotated between a polishing position for polishing samples and a wash position where it is over a wash and dry station, the platen transfer mechanism being operated when the polishing head is rotated to its wash position. The polishing head including the sample holder may be raised and lowered together as a unit by means of a telescopic driveshaft, i.e. the clearance between the polishing head and the sample holder is kept constant following the sample holder and polishing head's fixed connection to the shaft.
U.S. Pat. No. 4,771,578 A discloses an apparatus for grinding or polishing of workpieces, particularly metallographic samples. The grinding or polishing pressure is transmitted to the workpiece through a deformable transmission link which is strained by strain gauges of an activating member, which is then immobilized. The apparatus comprises means for sensing the elastic deformation of the transmission link and changes of that deformation during the progress of the process, whereby a simultaneous measurement of the grinding or polishing pressure and the depth of the layer of material removed by the grinding or polishing is obtained. The driveshaft, thrust housing and the sample holder are configured for moving vertically together as a unit.
U.S. Pat. No. 4,020,600 A discloses a high pressure polishing fixture assembly having a vertically movable pressure plate providing depending means for engagement with a plurality of workpiece-carrying heads position able under pressure upon a rotatable polishing plate. The thrust housing is in this assembly not mounted to the driveshaft.
U.S. Pat. No. 3,892,092 A discloses an automatic polishing apparatus for polishing the surface of a specimen for the purpose of microstructural analysis. The apparatus includes first and second eccentric drive means driven at different speeds from a single drive motor and acting through one end of a drive arm which is movable both pivotally and axially and is connected at its other outer end with a specimen holder so as to move a specimen through a multidirectional path over a flat, horizontal polishing surface. The thrust housing is in this apparatus not mounted to the driveshaft.
US 2014/0030967 A discloses a grinder/polisher provided with a specimen mover where the specimens are placed in a specimen mover plate. The reference teaches a grinder/polisher configured for positioning a drive a thrust housing and the specimen holder plate, as a unit, in a position relative to the rotating preparation surface. The grinder/polisher includes, housed within the head, a first drive for rotational drive of the specimen holder plate (a rotational drive) and a second drive for moving the head and the specimen holder, as a unit also including the specimen holder, vertically, towards and away from the preparation surface (a height drive).
The specimens are, in grinding and/or polishing machines of the kind to which the present invention relates, urged or pressed towards the preparation surface by means of thrust pads which, in a simple form, may constitute a form of linear actuator pressing the specimen against the preparation surface. The forces may stem from one or more springs, hydraulic pressure, pneumatic pressure etc. acting e.g. on one or more thrust pads via thrust rods.
In order to place, or insert, one or more specimens in a grinding and/or polishing machine comprising a specimen mover of the kind according to the present invention, the operator typically is required to push or manipulate, or push to retract, the thrust pads incl. thrust rods away from the preparation surface thereby providing an increased gap between the preparation surface and the thrust pad and specimen mover plate or cage. The increased gap allows for insertion and accommodation of the specimen in the specimen mover. This operation is hindered significantly by the specimen mover plate or cage which is provided with one or more openings in which the specimens reside when inserted in the specimen mover.
As the thrust pads often are configured for a limited distance of travel, placing relatively high specimens under a thrust pad is a difficult and time consuming operation. Typically, the operator is required to alter the length of the thrust rod by means of a threaded connection or similar allowing the thrust rod either to extend or retract from the thrust housing.
It is a problem of the prior art that these actions are hard or difficult to perform. Furthermore, manipulating the length of the thrust rod often results in varying resulting force applied to the specimen as the origin or properties of the forces typically change the resulting force in response to the manipulation or different lengths of the thrust rod. This results in difficulties in obtaining replicability in the preparation procedure as the specimens are pressed against the preparation surface with varying force following removal and insertion of the specimens.